1. Field of the Invention
The present invention relates to the repair, reshaping and cladding of superalloy components, and more particularly, to the weld build up of nickel base superalloy components containing relatively large amounts of aluminum and/or titanium, employing a hold and cool process so as to reduce susceptibility to cracking, and to the materials so produced.
2. Background and Related Art
Nickel base superalloys (also known as nickel based or nickel-based) are high-temperature materials which display excellent resistance to mechanical and chemical degradation of properties even as temperatures approach the melting points of the materials. Ni base superalloys are based upon nickel (Ni) and typically contain numerous other elements such as chromium (Cr), aluminum (Al), titanium (Ti), tungsten (W), cobalt (Co), tantalum (Ta), carbon (C), among others. Such high-temperature superalloys found early application in aircraft turbine engines. A higher operating temperature typically leads to increased fuel efficiency and lower carbon emissions, causing superalloys to find increasing uses in ground-bases turbine systems as well. For example, see The Superalloys, by Roger C. Reed, (Cambridge University Press, 2006, particularly Chapter 1. The entire contents of this reference is incorporated herein by reference for all purposes.
The Al and Ti content of Ni base superalloys is typically increased in order to improve the high temperature strength, but at the expense of introducing challenges in welding or weld buildup of such materials. Generally, increased Al and/or Ti content of a Ni base superalloy increases the susceptibility of the material to cracking during welding or weld build up. Our previous work in this field cited above addressed the improvement in the weld repair of such superalloys. The present work addresses the related problem of weld build up of material while reducing the susceptibility to cracking of the materials so constructed.
The reference cited above, Ser. No. 13/611,034 (U.S. Pat. No. 9,272,365) explicitly states that cracking typically becomes a problem for a superalloy having more than 6% aggregate aluminum or titanium content (Paragraph [0008] of Ser. No. 13/611,034 as filed and Col. 1, L. 43-47 of U.S. Pat. No. 9,272,365). For economy of language herein we refer to such alloys as having “significant titanium and aluminum content.”
Thus a need exists in the art for improved methods to build up Ni base superalloy materials by a weld build up process, typically a laser additive repair process, particularly for those superalloys including relatively large amounts of Al and/or Ti.